Vegetation reduces noise pollution through a phenomenon called sound attenuation, which is the reduction of sound intensity. Leaves, twigs, and branches on trees, shrubs, and herbaceous growth absorb  sound energy.

Loudness of sound means how much is the intensity of sound produced.

Sound is a mechanical wave.And mechanical waves needs a material medium to carry it's vibrations .So sound requires a medium to propagate.And vaccum is just empty space , it does not have any medium .So sound cannot pass through vaccum.

Sitar - In Sitar, the string vibrates and produces sound.

Larynx is the voice box inside human neck, which produces sound. Vocal cords are found inside larynx, and frequency of sound generated depends upon the thickness of vocal cords. Glottis makes several voicing sounds between the vocal folds, when they vibrate. So option (A), (B) and (C) can't be the answer.

Sound is a mechanical wave , it is defined as a disturbance which travels through a material medium due to repeated periodic vibrations of the particles of the medium about their mean position , the disturbance is transferred from one particle to the adjoining particle , without any net movement of medium .

Pitch is a perceptual property of sound which depends on the frequency of sound, hence if frequency becomes higher, pitch would also be higher.

$$Answer:-$$ C

  In flute and Siren , air is blown inside these instruments (energy is given) , and air inside them vibrates i.e. air column vibrates and sweet sound is produced .

Optic nerve carries the signal from eye to brain .

When the sticks hit on the surface of the membrane, the membrane vibrates and results in the production of sounds.

In flute or whistle, the air column inside vibrates and produces sound.

In a musical sound,  wave patterns are repeating whereas a noise has irregular wave patterns. As out of the given figure, we have irregular patterns in figure $$(d)$$, so it is a noise. 

Answer is D.

Sound is a form of energy produced and transmitted by vibrating matter. Sound travels in waves. When sound moves through matter (solid, liquid, or a gas), the molecules of the matter move backward and forward in the direction in which the wave is traveling. This movement is called a vibration. Sound travels more quickly through solids than through liquids and gases because the molecules of a solid are closer together. Sound travels the lowest through gases because the molecules of a gas are farthest apart. In a vacuum sound cannot travel because there is no matter for it to move through.
Hence, sounds can travel in solids, liquids and gases.

Below are the answers and the corresponding explanations.

(a) True. Sound requires a medium to travel through. Since vacuum is devoid of any medium, sound cannot travel through it.

(b) False. The number of oscillations per second of a vibrating object is known as its frequency. Time period is the time
required to complete one oscillation.

(c) False. Loudness of a sound is proportional to the square of the amplitude of its vibration. When the amplitude of
vibration of a sound is large, the sound is very loud. The sound is feeble for small amplitude.

(d) True. Humans cannot hear sounds of all frequencies. Human can hear a sound whose frequency falls in the range of
20 Hz - 20,000 Hz. The sound having frequency out of this range is inaudible to humans.

(e) False. The pitch of a sound is proportional to its frequency. As the frequency of vibration increases,
the pitch of the sound also increases and vice versa. A sound is said to be high pitched if its frequency of vibration is high
and is low pitched for a small frequency of vibration.

(f) False. Unwanted or unpleasant sounds are known as noise. Sounds that are melodious and pleasing to ear are known as music.

(g) True. Unwanted or unpleasant sounds are known as noise. If one is subjected to loud unpleasant sound
continuously for a long time, then it may cause temporary hearing impairment.

Hint: The time period is the inverse of the frequency.

Step – 1: Get relationship between frequency and time period

The time period is shown as,

So, $$time\ period = \dfrac{1}{frequency}$$

Step – 2: Put value in the equation 

Here, mosquito generates average rate of 500 vibrations per second. So, frequency will be 500.

$$time\ period = \dfrac{1}{frequency}$$

$$= \dfrac{1}{500}$$

 $$= 0.002\ second$$

$$Answer:$$

Hence, option A is the correct answer.

Answer is A.

The intensity or loudness of a sound depends upon the extent to which the sounding body vibrates, i.e., the amplitude of vibration. A sound is louder as the amplitude of vibration is greater. Loudness is measured in units called decibels.

Answer is C.

The top of the tabla drum is covered with a stretched, layered leather membrane held in place by leather braces. The wooden pegs between the braces and the drum adjust the tension in the braces, thus controlling the pitch of the instrument.
Hence, to increase the pitch of the sound produced the player tightens the skin by stretching the string around it.

The answer is B.

Amplitude is the maximum distance covered by an oscillating body. To complete one oscillation, the body has to start from the mean position, then goes to the maximum distance on one side, then comes back to the mean position, then goes to the maximum position on the other side, and finally comes back to the mean position.

Time Period (T) is the number of seconds per waveform, or the number of seconds per oscillation.  It is clear that frequency and period are reciprocals. 
In this case, A bicycle wheel spins 25 times in 5 seconds. 
That is, the frequency is given as $$f=\frac { 25 }{ 5 } =5Hz$$.
Time period = $$\frac { 1 }{ f } =\frac { 1 }{ 5 } =0.20s$$
Hence, the frequency is 5 Hz and the time period is 0.20 seconds.

The maximum amount that a particle moves away from its rest position is called amplitude.
Amplitude is the maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. It is equal to one-half the length of the vibration path. 
For a transverse wave, such as the wave on a plucked string, amplitude is measured by the maximum displacement of any point on the string from its position when the string is at rest. For a longitudinal wave, such as a sound wave, amplitude is measured by the maximum displacement of a particle from its position of equilibrium. 

Answer is B.

Sound needs something to travel through to get from one place to another. In the space, since there is no air, sound cannot travel above the surface. So, there are no sounds in the space. 
The space has no air because its gravity is too weak to hold an atmosphere. Hence, if an enemy spaceship exploded 'they will not hear anything as there is no medium for sound to travel, but they can see the explosion because light can travel through space as light needs no medium to travel.
Renu is correct.

Answer is A.

When tuning a violin, a string is tightened which means that the length of the string is shortened.
When the length of a string is changed, it will vibrate with a different frequency. Shorter strings have higher frequency and therefore higher pitch. When a musician presses his finger on a string, he shortens its length. The more fingers he adds to the string, the shorter he makes it, and the higher the pitch will be. That is, higher frequency. 
Hence, the statement is true.

Frequency is inverse of the time period ,